And TDKR's was so long because there was no 2nd unit, w/ Nolan shooting everything himself.

Just like Snyder is doing with this film.

Yep...
We also have to consider that with a bigger cast, some participants may have had prior commitments as well? Pushing the initial start date may have created some conflicts with scheduling?
Cast and/or crew members..

Filming in Detroit may also minimize the amount of stages available with enough size and space.. Thus, some sets may have to wait to be built on the same sound stages as sets that currently occupy the same space?

And they mentioned location filming as well?
Tough one to do through a summer... Closing down streets and locations during a summer can be a huge pain and inconvenience for those that live there...

A longer, more spread out production schedule can allow more flexibility through out the entire shoot. Allow these guys to do exactly what they want.. When.. And where..

Patience is, sometimes, a good thing with a project this big.. They have the money and time, so there should be no rush.

I would like them to take their time, and get it right.
Expectations are going to be very high on this one..